IIHS Top Safety Pick. Scores 24 Highway MPG and 17 City MPG! This GMC Terrain delivers a Gas/Ethanol V6 3.6L/217 engine powering this Automatic transmission. WHEELS. 4 - 19 X 7.5 (48.3 CM X 19.1 CM) DENALI-SPECIFIC. TRANSMISSION. 6-SPEED AUTOMATIC (STD). TIRES. P235/55R19... via V12 Software